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Astron. Astrophys. Suppl. Ser. 139, 625-628

Hyperfine population measurement of excited OH from H2O photodissociation by microwave stimulation - first results

T. Thissen 1 - H. Wurps 1 - H. Spiecker 1 - J.J. ter Meulen 2 - P. Andresen 1

Send offprint request: T. Thissen

Correspondence to: Angewandte Laserphysik, University of Bielefeld, Universitaetsstr. 25, 33615 Bielefeld, Germany.

1 - Angewandte Laserphysik, University of Bielefeld, Universitaetsstr. 25, D-33615 Bielefeld, Germany
2 - Department of Molecular and Laser Physics, University Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The Netherlands

Received February 17; accepted July 22, 1999


In this paper the first measurement of the hyperfine population of a photofragment is presented. The population of the hyperfine levels of the $^2\Pi _{3/2}(J=7/2)$ state of OH out of photodissociation of cold $\rm H_2O$ turns out to be statistical. After photodissociation of water at 157 nm within a Fabry-Perot microwave cavity the nascent OH formed in the v=0, J=7/2 state (probed by LIF) is stimulated by microwave radiation. From saturation data the population in each hyperfine level in both $\Lambda $-doublets is determined.

Key words: masers -- molecular data -- ISM:molecules -- radio lines: ISM

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